Leadframe packages are well known and widely used in the electronics industry to house, mount, and interconnect a variety of different integrated circuits (ICs). A conventional leadframe is typically die-stamped from a sheet of flat-stock metal, and includes a plurality of metal leads temporarily held together in a planar arrangement about a central region during package manufacture by a rectangular frame including a plurality of expendable “dam-bars.” A mounting die pad for a semiconductor die is supported in the central region by “tie-bars” that attach to the frame. The leads extend from a first end integral with the frame to an opposite second end adjacent to, but spaced apart from the die pad.
In a flip chip on leadframe package, an IC die having solder bumps on its bond pads on the topside of the die is flipped (topside/circuit side) onto a leadframe, where the die is bonded to the die pad and is electrically coupled to the wire bond pads through re-flowing of the solder bumps. One problem with flip chip on leadframe packages resulting in rejected devices is lack of solder ball attachment to the wire bond pads of the leadframe causing electrical opens which can occur due to lack of leadframe co-planarity. One solution to this problem involves increasing the solder ball size which can help somewhat to resolve this issue. However, increasing the solder ball size has disadvantages including an increased incidence of solder ball collapse and solder smearing which each can cause yield loss.